Unqualified, it is not unreasonable for 'English' to refer to the language spoken in England by the English people while 'American English' refers to the varian

Unqualified, it is not unreasonable for 'English' to refer to the language spoken in England by the English people while 'American English' refers to the variant spoken in the United States of America by the American people, just as Canadian English refers to the variant spoken elsewhere in North America in Canada by the Canadian people. It is especially reasonable when used this way by an English writer writing for a British publication.